How can I compute Omega Squared in Stata after an ANOVA? | Stata FAQ

After you perform an ANOVA, it is useful to be able to
report Omega Squared as a measure of the strength of the effect of the independent
variable. Stata does not have a program or option that computes this, but ATS has developed a program called
omega2 that you can download and use to
compute Omega Squared after running an ANOVA. You can download the omega2
command by typing search omega2 (see
How can I use the search command to search for programs and get additional
help? for more information about using search).

Once installed, you can use
omega2
after running an ANOVA. Below, we run an ANOVA where factor b has 4
levels and is highly significant.

When there is more than one factor present, you need to
supply omega2 with the SS and df for
the effect you wish to compute Omega Squared. Below, we compute Omega Squared for
factor b by supplying the SS and df for
factor b.